1. Field of the Invention
The present invention relates to a light measuring device for the single lens reflex camera for carrying out the so called direct light measurement in accordance to which the light reflected on the film plane or the shutter plane or both of them so as to measure the light amount in the field.
2. Description of the Prior Art
Generally, the systems with a single light sensing element in accordance to which the light measuring optical system between the light measuring object image forming plane (for example, the film plane or the focusing plane) and the light sensing element is changed so as to change over the light sensitivity distribution between the selective area light measurement and the average light measurement is already known.
In such systems as mentioned above there are two kinds, namely the one, in accordance to which two kinds of the light measuring optical systems arranged in front of the light sensing element are changed over so as to select the selective area or the average light measurement as is disclosed in Japanese Patent Laid-Open No. Sho 53-98821 and the other one in accordance to which a zoom lens is arranged in front of the light sensing element so as to vary the light sensitivity distribution on the focusing plane so as to select the selected area or the average light measurement as is disclosed in Japanese Patent Publication No. Sho 51-20899.
However, both of the above systems have a problem, because two kinds of the optical systems have to be made use of or the zoom optical system has to be made use of, which makes the production cost high or the size of the optical system large.
Especially in case of the direct light measurement, the light sensing means is generally arranged on the bottom of the dark space of the camera so that the size of the change over means of the light measurement range is a problem.